A hard disk drive includes a thin-film magnetic recording read/write head (TFH), a rotating disk with thin-film magnetic media, a spindle motor to drive the disk, an electromagnetic voice-coil rotary actuator with a gimbal suspension to move the slider across the disk surface, and electronics. The TFH consists of an inductive electromagnetic coil writer, a giant magnetoresistive (GMR) reader, and a slider body with an air-bearing surface, which flies over the magnetic disk to perform the read and write functions.
The TFH transducers are produced using a thin-film wafer-processing technology. TFH wafer processing is similar to that used in the fabrication of semiconductor devices, involving deposition, photolithography, etch, electroplating, and CMP.
In the inductive writer, the electromagnetic coil induces magnetic flux in the loops, and the magnetic field between two pole tips (write gap) writes information on a disk. The write gap determines the linear bit density. In the GMR reader, the magnetic field from the disk changes the resistance of the GMR sensor and indicates the transition information. The sensor gets the data back by seeing the vertical magnetic-field transition from the disk. The bottom shield S1 and the top shield S2 prevent the GMR sensor from responding to fields just before and immediately after the transition to improve the linear bit resolution. The distance between two shields is referred to as the read gap, which determines the linear density of reading. The GMR sensor effect is due to scattering between two magnetic layers—a free layer and a pinned layer. The free layer is a soft magnet and magnetization is free to rotate. The pinned layer is fixed by exchange coupling to an antiferromagnet and magnetization, which keeps it stationary. The resistance of the GMR head changes, depending upon the angle between the magnetization of two layers, due to the effect of magnetic field from the disk on the free layer. The antiferromagnetic exchange layer provides the pinning field to the pinned layer.
Magnetic read/write head design and fabrication technology are following the same trends as semiconductors. For the last several years, annual performance enhancement of read/write heads for magnetic data storage (areal density gigabits/in.2=linear density bits/in.×track density tracks/in.) has doubled each year. With shrinking device dimensions and new magnetic materials, critical dimensions in the read/write heads have actually become smaller than those in semiconductors.
One common approach of defining perpendicular head pole structure is to ion mill laminated magnetic film through some type of hard mask, which is usually formed by milling-resistant organic or inorganic material. Due to the nature of ion milling, fencing is formed on the sidewall of remaining hard mask. Conventional stripping processes like wet stripping or snow cleaning all have their disadvantages in removing the remaining hard mask, e.g., wet stripping has difficulty to completely remove the fencing and snow clean could easily bend the pole.
The top critical dimension (CD) of the pole for perpendicular head is the most critical head parameter. Any deterioration to the CD cannot be accepted. In fact, the fencing on the remaining hard mask sidewall is very thin, which is allowed to be left in head without degrading the pole's magnetic property. However, if the remaining hard mask is simply removed by wet stripping or dry stripping, the unsupported fence can easily collapse during stripping process or subsequent refill process and result in Alumina fill defect, which will result in reliability issue.
It can be seen that there is a need for a lift-off method for forming write pole of a magnetic write head and write pole formed thereby.